# EVM Transaction Simulator (eth_simulateV1)

> EVM Transaction Simulator (eth_simulateV1) is a paid API for AI agents from yonder-spotless-stranger.ngrok-free.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).

Simulates an EVM transaction on Ethereum mainnet or Base and returns revert status, revert reason, gas used, and real token balance deltas for all touched addresses.

## Facts

- Endpoint: POST https://yonder-spotless-stranger.ngrok-free.dev/simulate
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/evm-transaction-simulator-eth-simulatev1-37022e54
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_w5yTwAldTgmxTgnq_7Oxo

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability evm-transaction-simulator-eth-simulatev1-37022e54 -d '<json body>'
```

Example prompt: Before I submit this transaction, simulate it for me — the sender is 0xABC...123, the target contract is 0xDEF...456, calldata is 0xa9059cbb...000064, sending 0 wei on Ethereum mainnet — will it revert, how much gas will it use, and what token balances will actually change?

## When to prefer this

Use this endpoint when you need to know definitively whether a transaction will revert and why, or when you need accurate token balance deltas across all addresses — not just a gas estimate. Prefer this over eth_estimateGas when revert reasons or actual token flow visibility matters. Ideal before submitting any high-stakes DeFi, NFT, or contract interaction transaction on Ethereum mainnet or Base where wasted gas or unexpected outcomes are costly.

## Known failure modes

- Invalid or malformed address for 'to' or 'from' fields returns a validation error
- Unsupported chain value (not 'mainnet' or 'base') returns an error
- Malformed calldata hex causes simulation failure
- Transaction requires state not available on the node (e.g. future block) may fail or return inaccurate results
- Payment failure (insufficient USDC or x402 protocol error) blocks the call
- Node RPC timeout on complex traces may return an error

## How this service works

Pre-flight any EVM transaction and get back whether it reverts, the revert reason, gas used, and the REAL token balance deltas for every address it touches — from an eth_simulateV1 trace, not a gas estimate. Supports Ethereum mainnet and Base. Use it to kill a losing transaction before you pay gas for it.

## Output

Returns whether the transaction reverts, the human-readable revert reason if it does, the actual gas consumed, and a list of real token balance deltas (positive or negative) for every address touched by the transaction — derived from a full eth_simulateV1 execution trace, not a static estimate.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "to": {
   "type": "string",
   "description": "target contract or account"
  },
  "data": {
   "type": "string",
   "description": "calldata hex, optional"
  },
  "from": {
   "type": "string",
   "description": "sender address"
  },
  "chain": {
   "type": "string",
   "description": "mainnet or base"
  },
  "value": {
   "type": "string",
   "description": "wei, decimal string"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/evm-transaction-simulator-eth-simulatev1-37022e54/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from yonder-spotless-stranger.ngrok-free.dev](https://www.zero.xyz/host/yonder-spotless-stranger.ngrok-free.dev/llms.txt)